Applicant is aware of U.S. Pat. Nos. 2,870,446 to Mitchell; 3,225,459 to Wilstein and 3,629,870 to Paisley which show different designs of instrument flight training devices. However, none of these prior art Patents show an instrument training device that has the important structural features that give the advantages of the present invention.
U.S. Pat. No. 3,575,497 to Leblanc shows an example of sun glasses with a flip-up feature.
Another view limiting device currently used for instrument pilot training is sold under the trade name "Foggles". Foggles are basically conventional glasses frames with lenses that have the upper part made of tinted glass. These view limiting devices do not have the important features of applicant's device. Such view limiting devices are particularly uncomfortable when used with a radio head set.